1. Field of the Invention
The present invention relates to a metal material bonding method. More specifically, it relates to improvement in a metal material bonding method in which an insertion material is interposed between the metal materials to be bonded.
2. Description of the Related Art
Heretofore, a bonding method using an insertion material interposed between materials to be bonded to each other has been employed in liquid-phase diffusion bonding.
However, because the insertion material used is formed to have a shape and a size so as to cover the whole of bonding surfaces, there arises a problem that the insertion material is partially extruded between materials to be bonded at the time of bonding so that surfaces of the bonding portions of the materials to be bonded are covered with the insertion material. When the bonding portions are under such a condition, the insertion material extruded and solidified so as to cover the surfaces of the bonding portions of the materials to be bonded exerts a notching effect so that strength against fatigue of bonding is lowered. Therefore, the work of removing the insertion material covering the surfaces of the bonding portions of the materials to be bonded after bonding is required. There arises also a problem that this brings about lowering of productivity or workability.